Now I believe the last blocker depends on tghe qt libraries. Any idea how to resolve this?

I don't see any. Only pay attention to the 'B' blockers.

There is only one blocker left. Just `emerge -1 libproxy`? And if there's a strange blocker, add signond and signon-ui to the same upgrade command?_________________backend.cpp:92:2: warning: #warning TODO - this error message is about as useful as a cooling unit in the arctic

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

dev-qt/qtcore:5

(dev-qt/qtcore-5.7.1-r3:5/5.7::gentoo, ebuild scheduled for merge) pulled in by
~dev-qt/qtcore-5.7.1 required by (dev-qt/linguist-tools-5.7.1:5/5.7::gentoo, ebuild scheduled for merge)
^ ^^^^^
(and 1 more with the same problem)

(dev-qt/qtcore-5.9.2:5/5.9::gentoo, ebuild scheduled for merge) pulled in by
~dev-qt/qtcore-5.9.2 required by (dev-qt/qtgui-5.9.2:5/5.9::gentoo, ebuild scheduled for merge)
^ ^^^^^
(and 1 more with the same problem)

NOTE: Use the '--verbose-conflicts' option to display parents omitted above

It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously. If such a conflict exists in
the dependencies of two different packages, then those packages can
not be installed simultaneously.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.

* In order to avoid wasting time, backtracking has terminated early
* due to the above autounmask change(s). The --autounmask-backtrack=y
* option can be used to force further backtracking, but there is no
* guarantee that it will produce a solution.

!!! All ebuilds that could satisfy "~dev-qt/qtgui-5.7.1[gles2=]" have been masked.
!!! One of the following masked packages is required to complete your request:
- dev-qt/qtgui-5.7.1-r1::gentoo (masked by: backtracking: missing dependency)

(dependency required by "dev-qt/qtdeclarative-5.7.1-r1::gentoo" [ebuild])
(dependency required by "dev-qt/linguist-tools-5.7.1::gentoo[qml]" [ebuild])
(dependency required by "kde-frameworks/kconfig-5.37.0::gentoo[nls]" [ebuild])
(dependency required by "net-libs/libproxy-0.4.13-r2::gentoo[kde]" [ebuild])
(dependency required by "libproxy" [argument])
For more information, see the MASKED PACKAGES section in the emerge
man page or refer to the Gentoo Handbook.

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

dev-qt/qtgui:4

(dev-qt/qtgui-4.8.6-r4:4/4::gentoo, installed) pulled in by
~dev-qt/qtgui-4.8.6[-aqua,-debug,abi_x86_64(-)] required by (dev-qt/qthelp-4.8.6-r3:4/4::gentoo, installed)
^ ^^^^^
(and 2 more with the same problem)

(dev-qt/qtgui-4.8.7:4/4::gentoo, ebuild scheduled for merge) pulled in by
~dev-qt/qtgui-4.8.7[aqua=,debug=,glib=,qt3support,abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?,abi_ppc_32(-)?,abi_ppc_64(-)?,abi_s390_32(-)?,abi_s390_64(-)?] required by (dev-qt/qtcore-4.8.7-r3:4/4::gentoo, ebuild scheduled for merge)
^ ^^^^^
>=dev-qt/qtgui-4.8.7:4 required by (media-libs/phonon-vlc-0.9.1-r1:0/0::gentoo, ebuild scheduled for merge)
^^ ^^^^^^^
(and 7 more with the same problems)

dev-qt/qtcore:4

(dev-qt/qtcore-4.8.7-r3:4/4::gentoo, ebuild scheduled for merge) pulled in by
~dev-qt/qtcore-4.8.7[aqua=,debug=,abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?,abi_ppc_32(-)?,abi_ppc_64(-)?,abi_s390_32(-)?,abi_s390_64(-)?] required by (dev-qt/designer-4.8.7:4/4::gentoo, ebuild scheduled for merge)
^ ^^^^^
>=dev-qt/qtcore-4.8.7-r2:4 required by (media-libs/phonon-vlc-0.9.1-r1:0/0::gentoo, ebuild scheduled for merge)
^^ ^^^^^^^^^^
(and 13 more with the same problems)

(dev-qt/qtcore-4.8.6-r2:4/4::gentoo, installed) pulled in by
~dev-qt/qtcore-4.8.6[-aqua,-debug,glib,qt3support,abi_x86_64(-)] required by (dev-qt/qtgui-4.8.6-r4:4/4::gentoo, installed)
^ ^^^^^
(and 6 more with the same problem)

dev-qt/qtscript:4

(dev-qt/qtscript-4.8.7:4/4::gentoo, ebuild scheduled for merge) pulled in by
~dev-qt/qtscript-4.8.7[aqua=,debug=,abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?,abi_ppc_32(-)?,abi_ppc_64(-)?,abi_s390_32(-)?,abi_s390_64(-)?] required by (dev-qt/designer-4.8.7:4/4::gentoo, ebuild scheduled for merge)
^ ^^^^^
(and 2 more with the same problem)

(dev-qt/qt3support-4.8.7:4/4::gentoo, ebuild scheduled for merge) pulled in by
~dev-qt/qt3support-4.8.7[accessibility=,aqua=,debug=,abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?,abi_ppc_32(-)?,abi_ppc_64(-)?,abi_s390_32(-)?,abi_s390_64(-)?] required by (dev-qt/qtdeclarative-4.8.7:4/4::gentoo, ebuild scheduled for merge)
^ ^^^^^
(and 2 more with the same problem)

(dev-qt/qtsql-4.8.7-r1:4/4::gentoo, ebuild scheduled for merge) pulled in by
~dev-qt/qtsql-4.8.7[aqua=,debug=,qt3support=,abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?,abi_ppc_32(-)?,abi_ppc_64(-)?,abi_s390_32(-)?,abi_s390_64(-)?] required by (dev-qt/qtdeclarative-4.8.7:4/4::gentoo, ebuild scheduled for merge)
^ ^^^^^
(and 1 more with the same problem)

(dev-qt/qtsql-4.8.6-r1:4/4::gentoo, installed) pulled in by
~dev-qt/qtsql-4.8.6[-aqua,-debug,sqlite,abi_x86_64(-)] required by (dev-qt/qthelp-4.8.6-r3:4/4::gentoo, installed)
^ ^^^^^
(and 1 more with the same problem)

NOTE: Use the '--verbose-conflicts' option to display parents omitted above

It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously. If such a conflict exists in
the dependencies of two different packages, then those packages can
not be installed simultaneously.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.

It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously. If such a conflict exists in
the dependencies of two different packages, then those packages can
not be installed simultaneously.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.

Remove qttest:4 and qthelp:4, it seems they are not up for emerge but an old version is still lingering around, which may block your upgrade for that reason. You removed qtwebkit:4 already?_________________backend.cpp:92:2: warning: #warning TODO - this error message is about as useful as a cooling unit in the arctic

It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously. If such a conflict exists in
the dependencies of two different packages, then those packages can
not be installed simultaneously.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.